Subclusters on Kubernetes

Eon Mode uses subclusters for workload isolation and scaling. The VerticaDB operator provides tools to direct external client communications to specific subclusters, and automate scaling without stopping your database.

The custom resource definition (CRD) provides parameters that allow you to fine-tune each subcluster for specific workloads. For example, you can increase the subcluster size setting for increased throughput, or adjust the resource requests and limits to manage compute power. When you create a custom resource instance, the operator deploys each subcluster as a StatefulSet. Each StatefulSet has a service object, which allows an external client to connect to a specific subcluster.

Naming conventions

Kubernetes derives names for the subcluster Statefulset, service object, and pod from the subcluster name. This naming convention tightly couples the subcluster objects to help Kubernetes manage the cluster effectively. If you want to rename a subcluster, you must delete it from the CRD and redefine it so that the operator can create new objects with a derived name.

Kubernetes forms an object's fully qualified domain name (FQDN) with its resource type name, so resource type names must follow FQDN naming conventions. The underscore character ( "_" ) does not follow FQDN rules, but you can use it in the subcluster name. Vertica converts each underscore to a hyphen ( "-" ) in the FQDN for any object name derived from the subcluster name. For example, Vertica generates a default subcluster and names it default_subcluster, and then converts the corresponding portion of the derived object's FQDN to default-subcluster.

For additional naming guidelines, see the Kubernetes documentation.

External client connections

External clients can target specific subclusters that are fine-tuned to handle their workload. Each subcluster has a service object that handles external connections. To target multiple subclusters with a single service object, assign each subcluster the same spec.subclusters.serviceName value in the custom resource (CR). For implementation details, see VerticaDB custom resource definition.

The operator performs health monitoring that checks whether the Vertica daemon is running on each pod. If the daemon is running, then the operator allows the service object to route traffic to the pod.

By default, the service object derives its name from the custom resource name and the associated subcluster and uses the following format:

customResourceName-subclusterName

To override this default format, set the subclusters[i].serviceName CR parameter, which changes the format to the following:

metadata.name-serviceName

Vertica supports the following service object types:

• ClusterIP: The default service type. This service provides internal load balancing, and sets a stable IP and port that is accessible from within the subcluster only.

• NodePort: Provides external client access. You can specify a port number for each host node in the subcluster to open for client connections.

• LoadBalancer: Uses a cloud provider load balancer to create NodePort and ClusterIP services as needed. For details about implementation, see the Kubernetes documentation and your cloud provider documentation.

For configuration details, see VerticaDB custom resource definition.

Managing internal and external workloads

The Vertica StatefulSet is associated with an external service object. All external client requests are sent through this service object and load balanced among the pods in the cluster.

Import and export

Importing and exporting data between a cluster outside of Kubernetes requires that you expose the service with the NodePort or LoadBalancer service type and properly configure the network.